1. Field of the Invention
The present invention relates to a standard plane sample (also referred to as a standard plane sample for measuring device calibration, a specimen sample, or a reference plane sample) for supplying a measuring device with the reference data of the optical characteristic in an apparatus that measures the optical characteristic of a sample, and an optical characteristic measurement system in which such a standard plane sample and a measuring device are used as a set.
Specifically, the present invention relates to a standard color sample such as a standard white plate or color sample for supplying a calorimeter with reference data and a colorimetry system where such a standard color sample and a calorimeter are used as a set, or to a standard gloss sample such as a standard gloss sample or gloss specimen for supplying a glossmeter with reference data and a gloss measurement system in which such a standard gloss sample and a glossmeter are used as a set.
2. Description of the Related Art
In recent years, the importance of the color conditioning of products has come to be recognized in the fields of coating, molding, printing, fabric and the like. For this reason, measurement of the optical characteristic value such as measurement of the colors of products by use of a calorimeter is frequently performed in factories and the like.
In a case where a calorimeter is used, before measurement of the sample (object) to be measured is performed, calibration (user calibration) of the calorimeter is performed by use of a standard color sample, for example a standard white plate (hereinafter, referred to as white plate), annexed to the calorimeter.
Conventionally, the white plate is offered together with the calorimeter by the manufacturer. Normally, the white plate comes with calibration data or reference data obtained by actually measuring the reflectance (spectral reflectance) thereof. The calibration data is offered as printed matter such as paper, or as electric data stored in a storage medium such as a CD-ROM, a flexible disk or a memory card.
In order to input the calibration data of the white plate into the calorimeter, the data may be transferred from the storage medium every measurement. However, since this is onerous, normally, a nonvolatile memory is mounted in the calorimeter and the data is inputted when the colorimeter is purchased or when recalibration (value re-assignment, manufacturer calibration) of the white plate is-performed. Although the calibration data stored in the nonvolatile memory is, basically, not lost even when the colorimeter is turned off, it is necessary to input the calibration data again, for example, when the backup battery is exhausted.
The calibration using the white plate is to actually measure the reflectance (spectral reflectance) of the white plate. The calorimeter compares the actually measured value (actual measurement data) with the already read and stored calibration data (reflectance data) to calculate the correction coefficient, and multiplies the measurement data of the sample obtained thereafter by this correction coefficient. By such a calibration processing, the degradation in measurement accuracy due to fluctuations in the characteristic of the light source incorporated in the calorimeter can be suppressed.
Moreover, as the standard plane sample, some colorimetry applications use an arbitrary color sample (color tile, etc.) as well as the white plate.
While one calorimeter and one white plate constitute a set, when a plurality of calorimeters are provided, there are cases where which calorimeter and white plate constitute a set is uncertain. If a calorimeter is combined with a wrong white plate, the white plate not corresponding to the stored calibration data is actually measured in the calorimeter, so that an accurate correction coefficient cannot be obtained and accurate measurement cannot be performed also in this case.
Moreover, since inputting the calibration data into the colorimeter is not a frequency performed operation, the user has to look for the storage medium storing the calibration data when the operation is necessary, and there may be cases where the user cannot find the storage medium.
To cope with this problem, a colorimeter has conventionally been proposed in which a reference plate (white plate) for calibration is provided in the calorimeter and a measuring head is provided so as to be movable between the measurement position and the calibration position. That is, according to this calorimeter, at the time of the calibration, the measuring head is situated in the position of the reference plate for calibration inside the body, and at the time of the measurement of the object, the measuring head is moved to the position of the sample outside the body. By this, the calibration of white, R, G and B is automatically executed. By incorporating the white plate for calibration in the body, the white plate and the colorimeter can be integrally managed, so that it never occurs that a calorimeter is combined with a wrong white plate even when a plurality of calorimeters are provided.
The same problem as that of the above-described colorimetry system arises in the gloss measurement system. In a case where a glossmeter is used, before measurement of the sample (object) to be measured is performed, calibration (user calibration) of the glossmeter is performed by use of a standard gloss sample annexed to the glossmeter, and also with this standard gloss sample, the same problem as that of the standard white plate in the case of the calorimeter arises, that is, the following problem arises: the problem in the management of the standard gloss sample and the reference data thereof caused because the standard gloss sample and the reference data thereof are separately offered or the miscombination of the glossmeter and the standard gloss sample when the user has a plurality of glossmeters.
However, in the conventional calorimeter, since the white plate is integrally attached inside the calorimeter, the maintenance of the white plate is cumbersome. That is, the white plate becomes dirty due to use or deteriorates with time and this changes the reflectance thereof. While the amount of change differs according to the condition of use or the condition of storage, it is recommended to perform calibration (manufacturer calibration) every one to two years. In the calibration, the white plate is sent to the manufacturer, and the manufacturer re-measures the reflectance of the white plate, confirms the calibration data and performs recalibration (value re-assignment). This task is onerous in the structure of the calorimeter of the patent document 1.
Further, users are not sufficiently aware of the calibration of the white plate, and in many cases, even when the time when the calibration of the white plate must be performed comes, the user does not notice it and misses the opportunity of the calibration. Moreover, even when the user notices it, there are cases where the user cannot seize an opportunity to send the white plate for calibration and misses the opportunity. Consequently, there is a possibility that a condition where no calibration is performed continues over a long period of time.